Some people seem to have a level of natural immunity against the AIDS virus. And researchers are looking at their genes to try to help in the effort to make an HIV vaccine. That’s according to research reported in the current issue of the journal Science.

An international team of researchers examined almost 500 people infected with HIV, and identified a form of a gene that appears to have helped some of them fight off the virus, and delay the onset of AIDS. The unusual gene doesn’t stop infection, but it does keep the virus from proliferating.

Ordinarily, the immune system identifies invaders and marks them for destruction. But HIV can usually disarm two forms of the gene involved in identifying the intruders. Those two forms are called HLA-A and HLA-B. However, HIV doesn’t seem to be able to turn off a third form, HLA-C, and infected cells do get destroyed. Researchers hope a vaccine might mimic HLA-C’s effect.

Investigators say that a series of future genome-wide studies will seek to pinpoint additional targets for HIV vaccines.